The performance of micro-electronic devices has always been limited by the variations found in the dimensions of their critical features, termed critical dimensions or CD. Micro-electronic devices are often manufactured using masks (or reticles) in a photolithography process. The latter is one of the principal processes in the manufacture of semiconductor devices, and consists of patterning the wafer's surface in accordance with the circuit design of the semiconductor devices to be produced. Such a circuit design is first patterned on a mask. Hence, in order to obtain operating semiconductor devices, the mask must be defect free. Moreover, the mask is often used in a repeated manner to create many dies on the wafer. Thus, any defect on the mask will be repeated multiple times on the wafer and will cause multiple devices to be defective. Establishing a production-worthy process requires tight control of the overall lithography process. Within this process, CD control is a determining factor with respect to device performance and yield.
When the critical dimensions are large, systematic variations in the dimensions of the device, such as those caused by material physics or as a result of equipment or the production process, do not make large contributions to the overall error budget and can therefore be largely ignored. However, as the minimum size of critical features drops below about 65 nm, systematic variations that were previously ignored can now consume a considerable portion of the overall error budget. Specifically, systematic mask CD errors can consume over 50% of the total wafer lithography process CD budget.
Typical CD measurements are time consuming and involve complex image processing schemes of images that include a large number of pixels.
There is a need to provide efficient systems and methods for evaluating an evaluated pattern of a mask.